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Growth hormone-binding protein in human lymph
H Maheshwari1, S Lillioja, C E Castillo
1Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA.
The Journal of Clinical Endocrinology and Metabolism
|December 1, 1995
Summary
Growth hormone-binding protein (GHBP) is lower in lymph than plasma, indicating central organs like the liver are primary sources. Vascular cells do not produce significant GHBP.
Area of Science:
- Endocrinology
- Physiology
Background:
- The high-affinity GH-binding protein (GHBP) is the soluble ectodomain of the GH receptor (GHR).
- GHBP modulates GH action through intravascular and interstitial complex formation.
- The tissue sources and local regulation of GHBP remain largely unknown.
Purpose of the Study:
- To investigate GHBP levels in peripheral lymph, approximating interstitial fluid.
- To identify potential GHBP production by vascular cells.
- To understand GHBP distribution between circulation and interstitial space.
Main Methods:
- Collected peripheral lymph, venous, and arterial blood from healthy adult males.
- Assessed GHBP levels using a GH binding/column chromatography assay.
- Examined conditioned media from endothelial and blood cell cultures for GHBP production.
Main Results:
- GHBP levels were significantly lower in lymph compared to both venous and arterial plasma.
- Endothelial and blood cell cultures did not produce detectable GHBP.
- Lymph GHBP concentration was approximately 32% of plasma levels.
Conclusions:
- Peripheral lymph GHBP levels are substantially lower than circulating plasma levels.
- Vascular components are not significant sources of GHBP.
- Central organs, particularly the liver, are likely the primary sources of GHBP, with restricted transcapillary diffusion into the interstitial space.